Income is the consumption and savings opportunity gained by an entity within a specified timeframe, which is generally expressed in monetary terms.[1][2][3] However, for households and individuals, "income is the sum of all the wages, salaries, profits, interests payments, rents, and other forms of earnings received... in a given period of time."[4]

In the field of public economics, the term may refer to the accumulation of both monetary and non-monetary consumption ability, with the former (monetary) being used as a proxy for total income.

Total Income can be defined as sum of revenue earned - expenses. Income can be used to increase the growth of assets.

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Income per capita has been increasing steadily in almost every country.[5] Many factors contribute to people having a higher income such as education,[6]globalisation and favorable political circumstances such as economic freedom and peace. Increase in income also tends to lead to people choosing to work less hours. Developed countries (defined as countries with a "developed economy") have higher incomes as opposed to developing countries tending to have lower incomes.

In economics, "factor income" is the return accruing for a person, or a nation, derived from the "factors of production": rental income, wages generated by labor, the interest created by capital, and profits from entrepreneurial ventures.[7]

In consumer theory 'income' is another name for the "budget constraint," an amount Y{\displaystyle Y} to be spent on different goods x and y in quantities x{\displaystyle x} and y{\displaystyle y} at prices Px{\displaystyle P_{x}} and Py{\displaystyle P_{y}}. The basic equation for this is

Y=Px⋅x+Py⋅y{\displaystyle Y=P_{x}\cdot x+P_{y}\cdot y}

This equation implies two things. First buying one more unit of good x implies buying PxPy{\displaystyle {\frac {P_{x}}{P_{y}}}} less units of good y. So, PxPy{\displaystyle {\frac {P_{x}}{P_{y}}}} is the relative price of a unit of x as to the number of units given up in y. Second, if the price of x falls for a fixed Y{\displaystyle Y}, then its relative price falls. The usual hypothesis is that the quantity demanded of x would increase at the lower price, the law of demand. The generalization to more than two goods consists of modelling y as a composite good.

The theoretical generalization to more than one period is a multi-period wealth and income constraint. For example, the same person can gain more productive skills or acquire more productive income-earning assets to earn a higher income. In the multi-period case, something might also happen to the economy beyond the control of the individual to reduce (or increase) the flow of income. Changing measured income and its relation to consumption over time might be modeled accordingly, such as in the permanent income hypothesis.

"Full income" refers to the accumulation of both the monetary and the non-monetary consumption-ability of any given entity, such as a person or a household. According to what the economist Nicholas Barr describes as the "classical definition of income" (the 1938 Haig-Simons definition): "income may be defined as the... sum of (1) the market value of rights exercised in consumption and (2) the change in the value of the store of property rights..." Since the consumption potential of non-monetary goods, such as leisure, cannot be measured, monetary income may be thought of as a proxy for full income.[3] As such, however, it is criticized[by whom?] for being unreliable, i.e. failing to accurately reflect affluence (and thus the consumption opportunities) of any given agent. It omits the utility a person may derive from non-monetary income and, on a macroeconomic level, fails to accurately chart social welfare. According to Barr, "in practice money income as a proportion of total income varies widely and unsystematically. Non-observability of full-income prevent a complete characterization of the individual opportunity set, forcing us to use the unreliable yardstick of money income.

Income inequality refers to the extent to which income is distributed in an uneven manner. It can be measured by various methods, including the Lorenz curve and the Gini coefficient. Economists generally agree that certain amounts of inequality are necessary and desirable but that excessive inequality leads to efficiency problems and social injustice.[3]

Some scholars have come to the conclusion that material progress and prosperity, as manifested in continuous income growth at both the individual and the national level, provide the indispensable foundation for sustaining any kind of morality. This argument was explicitly given by Adam Smith in his Theory of Moral Sentiments[citation needed], and has more recently been developed by Harvard economist Benjamin Friedman in his book The Moral Consequences of Economic Growth.[citation needed]

The International Accounting Standards Board (IASB) uses the following definition: "Income is increases in economic benefits during the accounting period in the form of inflows or enhancements of assets or decreases of liabilities that result in increases in equity, other than those relating to contributions from equity participants." [F.70] (IFRS Framework).

According to John Hicks' definitions, income "is the maximum amount which can be spent during a period if there is to be an expectation of maintaining intact, the capital value of prospective receipts (in money terms)”.[8]

^Smith's financial dictionary. Smith, Howard Irving. 1908. Income is defined as, "Revenue; the amount of money coming to a person or a corporation (usually interpreted as meaning annually) whether as payment for services or as interest or other profit from investment."

^Webster's new modern English dictionary, illustrated. Webster, Noah. 1922. Income is defined as "the gain which proceeds from labor, business, property or capital; annual receipts of a person or corporation."

^ abcdBarr, N. (2004). Problems and definition of measurement. In Economics of the welfare state. New York: Oxford University Press. pp. 121-124